(1) Field of the Invention
The present invention generally relates to a device for throttling a flow of fluid and more particularly to a single piece plate to be used within said device. The flow throttling device may be used with a variety of onboard marine vessel systems including torpedoes, missiles and countermeasure tube systems.
(2) Description of the Prior Art
A cascade orificial resistive device (CORD) is a device which throttles pressurized water down to an acceptable flow rate. A cord utilizes a series of perforated plates passing the flow through the plate so as to create an incremental pressure drop across each plate. CORDS are currently used in numerous locations onboard marines vessels for the purpose of quieting flow by reducing flow rates.
Currently, all CORDS are similarly designed. FIGS. 1-5 illustrate a typical CORD construction. As shown therein, prior art CORDS have a metallic body 10 with an end ring 12 welded to the body and a metallic plate assembly assembled within the body 10 adjacent the ring 12. The plate assembly consists of a threaded rod 14, a plurality of perforated plates 16 positioned on the rod and separated from each other and from body 10 by spacer rings 18 and intermediate nuts 20 and washers 22. The assembly is clamped within the body 10 by a threaded end ring 24 on the inlet side 26 of the CORD.
The number of internal parts for a typical 30 plate CORD assembly manufactured in this fashion is 152. Each one of these 152 parts is a non-standard part and must be accurately machined. The perforated plates have a designed hole pattern which does not correspond to standard perforated plate. The spacer rings have close tolerance outside diameters and machine grooves on both sides. Even the nuts are individually machined to insure that their faces are parallel to each other and perpendicular to the center line.
Assembly is very critical to the performance of a standard CORD. For proper operation, all adjacent plates must have misaligned orifice holes in them. Currently, that is achieved by utilizing two differently designed plates. The center hole on each of these plates is keyed to the threaded rod. An assembler must alternate plates to maintain hole misalignment. Further difficulties with the standard system is that close tolerance machining is required to insure precise fitment of the various CORD components. When the components are precisely fitted together, resonances can be avoided. One of the difficulties, however, with the prior art systems, are that plates in the bolted assembly are often not tightly connected together. As a result, vibrations tend to occur during the flow. The metal to metal vibration which occurs can excite the wall of the CORD body and create both structureborne and liquidborne noise.